JP2024015997A - VoLTE-INTERWORKING FUNCTIONALITY FOR OUTBOUND ROAMING - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a system for providing interworking functionality (IWF) between VoLTE, circuit-switched voice, and an SMS service for outbound roaming.

SOLUTION: There are provided a system and method for implementing VoLTE, circuit-switched voice, and SMS interworking functionality in order to provide voice and SMS for a roaming mobile device in a network to be visited on the basis of circuit switching (CS) roaming towards VPLMN as well as SMS roaming towards HPLMN.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to interworking functionality for VoLTE-outbound roaming.

TECHNICAL FIELD The present invention relates generally to the field of Internet Protocol (IP) and telecommunications networks, and specifically to voice long-term evolution (VoLTE), circuit switched (CS) voice communication in outbound roaming environments from mobile operators. , and interworking across Short Message Service (SMS).

Circuit switched (CS) voice is a common technology for providing voice and SMS services to mobile networks in roaming environments. All 2G and 3G networks use CS to provide voice and SMS services. In order to use CS for roaming, both the visitor and the home operator need to be equipped with CS network components (MSC, HLR, etc.) and can support mobile originating (MO) and mobile terminating (MT) voice calls and SMS. Provide both.

In the 4G environment, a new technology has been invented, known as Voice Services in Long Term Evolution (LTE, "4G"), which is based on IP Multimedia Subsystem (IMS) technology and infrastructure. Both voice and SMS are supported via IMS.

With VoLTE and IMS infrastructure, mobile network operators no longer need CS infrastructure to provide voice and SMS services to subscribers within their domestic home networks. Many network operators are planning to shut down their 2G/3G network infrastructure to save spectrum for 4G and 5G services as well as reduce operating and maintenance costs.

However, the premise of utilizing VoLTE roaming is that the home operator requires a VoLTE roaming agreement with the visitor operator. Unfortunately this is very uncommon. Many visitor operators do not have IMS infrastructure or do not want to offer VoLTE roaming to their subscribers in order to protect their voice and SMS roaming revenue. This creates problems for home operators trying to implement VoLTE roaming. Therefore, these mobile providers are unable to shut down their 3G roaming network infrastructure. Similar issues arise as well for LTE-only operators that do not have 2G/3G infrastructure, preventing them from providing voice and SMS services to outbound roaming to visitor operators without VoLTE roaming. .

The current state of the technology requires methods and systems for providing interworking functionality (IWF) between VoLTE, circuit-switched voice, and SMS services for outbound roaming.

The present invention enables outbound roamers to use circuit-switched voice and SMS services in a visited public land mobile network (HPLMN) without the need for a VoLTE roaming agreement with a home public land mobile network (HPLMN) operator. It is related to IWF (interworking function) that makes it possible to do this. IWF operates as circuit switched (CS) roaming for VPLMN and as VoLTE roaming for HPLMN.

In one embodiment, the IWF includes the following functions: (1) Diameter Routing Agent (DRA) provides diamiter s6a/s6d between the VPLMN Mobility Management Entity (MME) and the HPLMN Home Subscriber Server (HSS). Intercept and route messages. (2) The Virtual Home Location Register (vHLR) provides subscriber registration services to the Mobile Switching Center (MSC) in the VPLMN. (3) The Virtual Mobility Management Entity (vMME) performs LTE registration with the HSS in the HPLMN. (4) A virtual short message service center (vSMSC) receives and routes mobile-originated SMS (MO-SMS) from a mobile device and routes mobile-terminated SMS (MT-SMS) to the mobile device. To deliver. (5) A virtual gateway mobile switching center (vGMSC) delivers mobile terminated calls (MT-calls) to user equipment (UE). (6) The Serving Gateway (SGW) encapsulates the IP packet into a General Packet Wireless Service Tunneling Protocol (GTP) tunnel towards the Packet Data Network Gateway (PGW) in the HPLMN. (7) The Interconnect Border Control Function (IBCF) acts as a border controller to the Public Switched Telephone Network (PSTN) connection.

In one embodiment, the DRA within the IWF provides Diameter Update-Location Request (ULR) and update information between the VPLMN Mobility Management Entity (MME) and the HPLMN Home Subscriber Server (HSS) during 4G network attachment. - Intercept location answer (ULA) messages. The DRA replaces the MME hostname in the ULR message with the hostname of the vMME so that subsequent HSS activation messages (eg, cancellation location requests, etc.) are received and processed by the vMME.

In a 4G network attachment, if the vHLR receives a MAP-Update-Location Request from the MSC/VLR, the vMME builds a Diameter S6a ULR Request to the HSS. Upon receiving the ULA, the vMME sends a Sh User-Data-Request (UDR) to the HSS to retrieve the multimedia telephony (MMTEL) service subscribed by the Roma. These MMTEL services are later used to build MAP insert-subscriber-data requests to the MSC/VLR in response to MAP-update-location requests.

In a 3G network attachment, if the vHLR receives a MAP-Send-Authentication-Information-Request MSC/VLR or Serving GPRS Support Node (SGSN), the vMME sends a Diamiter S6a Authentication-Information-Request to the HSS for authentication. (AIR) Construct message. When the vMME receives the Authentication-Information-Answer (AIA) message, the vHLR sends a MAP-Send-Authentication-Information-Response to the MSC/VLR or SGSN. When the vHLR receives the MAP-UPDATE-GPRS-LOCATION REQUEST from the MSC/VLR, the vMME constructs a Diameter S6a ULR request to the HSS. Upon receiving the ULA, the vMME sends a Sh User-Data-Request (UDR) to the HSS to retrieve the Multimedia Telephone (MMTEL) service subscribed to by the roamer. These MMTEL services are later used to construct a MAP insert-join-data request to the MSC/VLR in response to a subsequent MAP-update-location request from the MSC/VLR.

The vMME instructs the SGW to establish a GTP session with the HPLMN PGW for the "ims" access point name (APN) used to carry VoLTE voice and SMS traffic. The vMME then instructs the SGW to send a SIP registration request to the IMS core at HPLMN for IMS registration. The IMS core uses "early IMS authentication" (ref: 3GPP TS 33.978 session 6.1), which trusts user traffic from the GTP tunnel and skips "multimedia authentication-request/response" processing. configured to do so. Instead, the IWF's SGW or the Proxy-Call Session Control Function (P-CSCF) in the HPLMN IMS Core inserts an "authentication-complete" parameter in the SIP registration request. The Serving Call Session Control Function (S-CSCF) is responsible for completing the authentication (see: 3GPP TS 24.229 Section 5.4.1.2.2E).

Mobile originated (MO) voice calls from mobile devices are accomplished by the VPLMN MSC, which receives the CS call setup request from the UE and breaks out to its PSTN provider. This follows standard handling of MO voice calls in CS roaming status. The HPLMN is not involved unless a customized application for mobile network enhancement logic (CAMEL) triggers is activated at the visiting MSC.

Mobile Terminated (MT) voice to the UE consists of the following aspects. (1) The MT call arrives at the HPLMN IMS core where the subscriber is IMS registered. The IMS Core routes the SIP Invite to the UE (where its contact header was previously registered with the IMS Core during IMS registration) via the PGW, SGW, vGMSC. (2) The vGMSC queries the vHLR for MAP-Send-Routing-Information (SRI). (3) The vHLR queries the VPLMN MSC for the Mobile Station Roaming Number (MSRN) for the MAP-Provided-Roaming Number (PRN). (4) When the MSRN is received from the MSC, the vGMSC routes the call to the PSTN with the called party number (SIP request-URI and "To" header) being the MSRN. (5) The call arrives at the VPLMN MSC (assigned the MSRN number), and the VPLMN MSC routes the call to the UE with a CS call setup.

Mobile originated (MO) SMS consists of the following aspects. (1) The VPLMN MSC receives an SMS submit request from the UE via the Radio Access Network (RAN) and sends the request to the vSMSC via the MAP-MO-Forward-SM (MO-FSM). (2) The vSMSC converts the request into a SIP message and routes it to the IP Short Message Gateway (IPSMGW) of the SGW, PGW, HPLMNIMS Core, Telephone Application Server (TAS). (3) The IPSMGW routes the SMS request to the local SMSC or SMS gateway for delivery to the recipient.

Mobile Terminated (MT) SMS consists of the following aspects. (1) The IPSMGW in the HPLMN receives the MT-SMS and routes it to the IMS core in the form of a SIP message request. (2) The IMS Core routes the SIP message request to the UE (whose contact header was previously registered with the IMS Core during IMS registration) via the PGW, SGW, vSMSC. (3) The vSMSC sends a MAP-Send-Routing-Information-for-SM (SRI-SM) to the vHLR responsive to the VPLMN MSC address. (4) The vSMSC converts the SMS request into a MAP-MT-Forward SM (MT-FSM) and sends it to the MSC. (5) The MSC delivers the SMS to the UE via a radio access network (RAN).

For a thorough understanding of the invention, reference should be made to the following detailed disclosure in conjunction with the accompanying drawings.

FIG. 1 is a block diagram schematically illustrating the conceptual architecture of the VoLTE Outbound Roaming Interworking Function (IWF). The IWF operates as circuit switched (CS) voice/SMS roaming roaming towards VPLMN and packet switched (PS) VoLTE roaming towards HPLMN.

FIG. 2 is a signal diagram schematically showing the system architecture of the IWF.

FIG. 3 is a signal diagram schematically illustrating the call flow of a 3G network attachment in a VPLMN.

FIG. 4 is a signal diagram schematically illustrating the call flow for 4G network attachment in VPLMN.

FIG. 5 is a signal diagram schematically showing a call flow of MO-voice service using IWF.

6A and 6B are signal diagrams schematically showing a call flow of an MT-voice service using IWF.

FIG. 7 is a signal diagram schematically illustrating the call flow for MO-SMS service using IWF.

FIG. 8 is a signal diagram schematically showing a call flow of an MT-SMS service using IWF.

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, in which there is shown by way of illustration certain embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and changes may be made without departing from the scope of the invention.

FIG. 1 provides a schematic diagram of an embodiment of the invention. An interworking function (IWF) 10 is deployed between a visited public land mobile network (VPLMN) 50 and a home public land mobile network (HPLMN) 60. VPLMN 50 is a circuit switched (CS) network (eg, 2G, 3G network) and HPLMN 60 is a packet switched (PS) network, such as 4G Long Term Evolution (LTE) or 5G network. In the current state of technology, HPLMNs with LTE-only networks do not have the infrastructure or capability to do CS roaming, and VoLTE roaming is mandatory. A major limitation of VoLTE roaming is that the VPLMN and HPLMN must have an existing agreement with each other, which is impractical for many network providers.

The present invention, in one embodiment, addresses this problem by providing IWF 20 that communicates with both VPLMN 50 and HPLMN 60. IWF 20 enables HPLMN 60 to provide voice and SMS roaming services to subscribers roaming with VPLMN 50 without requiring CS capabilities of HPLMN 60 or a VoLTE roaming agreement with VPLMN 50.

The IWF 20 is equipped with a virtual home location register (HLR), a virtual GMSC and an SMSC, which act like a CS roaming towards the VPLMN 50. It also includes a virtual mobile management entity (MME) for LTE roaming towards the HPLMN 60. The IMS core within HPLMN 60 is utilized to receive Mobile Terminated (MT) MT-Voice and MT-SMS and route requests to IWF 20 into CS roaming 30 for UE roaming to reach VPLMN 50.

FIG. 2 shows a roaming user equipment (UE) 70 establishing a connection to the UTRAN 80 or EUTRAN 90 of the VPLMN 50. UE 70 is a subscriber of HPLMN 60 roaming in VPLMN 50. As mentioned above, VPLMN 50 is a 3G CS network or a 4G network that supports CS fallback. VPLMN 50 includes UTRAN 80 (for 3G), EUTRAN 90 (for 4G), Mobility Management Entity (MME) 100, and Mobile Switching Center (MSC) 110.

The IWF 20 then includes a Diameter Routing Agent (DRA) 120, a Virtual Home Location Register (vHLR) 130, a Virtual Short Message Service Center (vSMSC) 140, and a Virtual Gateway Mobile Switching Center (GMSC) 150. , a virtual mobility management entity (vMME) 160 , a serving gateway (SGW) 170 , and an interconnection border control function (IBCF) 180 .

The HPLMN 60 includes a Home Subscriber Server (HSS) 190, a Short Message Service Center (SMSC) 200, an IP Multimedia Subsystem (IMS) Core 210, a Telephone Application Server (TAS) 220, and a Packet... It includes a data network gateway (PGW) 230 and a policy and charging rules function (PCRF) 240. The IMS core 210 includes a proxy call session control function (P-CSCF), an inquiry call session control function (I-CSCF), and a serving call session control function (S-CSCF). Collectively, they are referred to as P/I/S-CSCF.

IWF 20 communicates with both VPLMN 50 and HPLMN 60. The DRA 120 of the IWF 20 is communicatively connected to the MME 100 of the HPLMN 50 and the HSS 190 of the HPLMN 60 via the s6a interface. DRA 120 is configured to intercept Update Location Request (ULR) and/or Update Location Answer (ULA) messages exchanged between MME 100 and HSS 190. DRA 120 may be configured to mediate intercepted ULR/ULA messages. DRA 120 mediates the ULR message so that the hostname of VMME 160 (instead of VPLMN MME 100) is stored in HSS 190.

IWF 20's vHLR 130 communicates with VPLMN 50's MSC 110 using the Mobile Application Part (MAP) protocol. IWF 20 uses vHLR 130 to establish a circuit switched (CS) connection with VPLMN 50. This is accomplished by the MSC/VLR triggering a MAP-location-update procedure on the vHLR 130 to update the MSC/VLR's global title (GT) address within the vHLR 130. In subsequent mobile terminated (MT) voice calls and SMS messages, vHLR 130 returns the MSC/VLR's GT for the UE.

The SGW 170 of the IWF 20 enables GPRS tunneling protocol (GTP) connectivity between the IMS core 210 and the HPLM NP GW 230 connected to the PCRF. In this manner, UE 310 may make a mobile originated (MO) voice call 250 using CS technology. IWF 20 converts this to packet-switched SIP/RTP 260 via SGW 170, PGW 230, and IMS core 210. IMS core 210 breaks out MO voice call 250 to PSTN 270 to reach destination party 280.

The SGW 170 of the IWF 20 enables MT-voice roaming services for the UE by bridging the MT-call 300 to its PSTN 290 via the Interconnection Border Control Function (IBCF) 180.

The MSC 110 of the VPLMN 50 and the vSMSC 140 of the IWF 20 are connected via MAP/SS7. This connection enables the VPLMN 50 to use CS-based SMS submission and delivery techniques to provide MO and MT SMS roaming services to the UE.

network attachment

Figure 3 shows the signal flow for a 3G network attachment using IWF20. UE 70 submits a network attach request to SGSN 105 in VPLMN 50, whereby the network attach request triggers a MAP-Send-Authentication-Information request to vHLR 130. VHLR 130 and vMME 160 convert the MAP-Send-Authentication-Information Request into a Diameter s6a Authentication-Information-Request (AIR) to HSS 190. HSS 190 returns an Authentication-Information-Answer (AIA). VMME 160 and vHLR 130 convert the Authentication-Information-Answer (AIA) into a MAP-Send-Authentication-Information result to SGSN 105 .

SGSN 105 then sends a MAP-UPDATE-GPRS-LOCATION REQUEST to vHLR 130. The vHLR 130 and vMME 160 convert the MAP-Update-Gprs-Location Request into a Diameter s6a Update-Location Request (ULR) to the HSS 190. HSS 190 returns an Update-Location Answer (ULA). VMME 160 and vHLR 130 convert the update-location answer (ULA) into a MAP-update-Gprs-location result to SGSN 105.

Next, vML 160 sends a Diameter Sh User-Data Request (UDR) to HSS 190 to retrieve the subscriber's MMTEL telephone service subscription. HSS 190 responds with UDA (User-Data-Answer) using MMTEL service subscriptions such as call forwarding and call barring. Such information is stored in IWF 20 for constructing an insert subscriber-data request to MSC 110 of VPLMN 50 .

MSC/VLR 110 within VPLMN 50 then sends a MAP-UPDATE-LOCATION REQUEST to vHLR 130. That VHLR 130 sends a MAP insert-subscriber-data request to the MSC/VLR 110 along with the MMTEL service subscription retrieved from the HSS 190 in the previous step. MSC/VLR 110 responds with a MAP-Insert-Subscriber-Data result and vHLR 130 sends a MAP-Update-Location result to MSC/VLR 110 to complete the network registration to UE 70.

IWF 20 then triggers SGW 170 to establish a Packet Data Protocol (PDP) context and an "ims" tunnel by sending a GTP-C create-session-request. This GTP tunnel is later used to carry voice and SMS traffic. PGW 230 sends a Gx Credit Control Request (CCR) to PCRF 240, which responds with a Credit Control Answer (CCA). PGW 230 sends a GTP-C create-session-response to SGW 170, and PDP context configuration is completed.

IWF 20 then triggers SGW 170 to send a SIP registration request to the IMS core via PGW 230 to register the virtual UE in the IMS domain. This registration is required for the IMS core to route MT-Voice and SMS to the virtual UE via PGW 230 and SG 170. The IMS Core approves the subscriber registration by sending a Cx User-Authorization-Request (UAR) to HSS 190, and HSS 190 responds with a User-Authorization Answer (UAA). In the embodiment of FIG. 3, the IMS core performs "early IMS authentication" by delegating SIP registration requests from SGW 170 of IWF 20. IWF 20 uses the Sh User-Data Request/Answer (UDR/UDA) to trigger TAS 220 to retrieve the subscriber MMTEL profile. SIP registration is completed by the IMS core sending a 200 OK to the SGW 170.

In another embodiment, the SGW 170 of the IWF 20 or the P-CSCF 210 of the HPLMN 60 IMS core inserts an "authentication-complete" parameter into the SIP registration request, and the serving call session control function (S-CSCF) 210 indicates that the authentication is complete. Assume that

Figure 4 shows the signal flow for a 4G network attachment using IWF20. The UE 70 submits a network attach request (combined EPS/IMSI attachment) to the MME 100 within the VPLMN 50, which triggers a Diameter-s6a Authentication-Information-Request (AIR) to the HSS 190, which request is sent within the IWF 20. HSS 190 responds with an Authentication-Information-Answer (AIA).

The MME 100 then sends a diamiter-s6a update-location request (ULR) to the HSS 190, which is intercepted by the DRA 120 at the IWF 20, which determines that subsequent HSS-initiated requests (such as cancel-location) will be sent to the vMME 160. HSS 190 responds with an Update-Location Answer (ULA).

Next, the MME 100 causes the SGW 171 to establish a PDP context and a GTP tunnel for the default Internet access APN by sending a GTP-C create-session-request. That GTP tunnel is used to carry Internet traffic and is not related to voice or SMS.

The MME 100 then causes the MSC 110 to send a MAP-UPDATE-LOCATION REQUEST to the vHLR 130, following the combined EPS/IMSI attachment process, and the vHLR/VMML sends a DIAMITER-S6A UPDATE-LOCATION REQUEST (ULR) to the HSS 190. ) and the HSS 190 responds with an Update Location Answer (ULA).

Next, vMME 160 sends a Diameter-Sh User-Data Request (UDR) to HSS 190 to retrieve the subscriber's MMTEL telephone service subscription. HSS 190 responds with UDA (User-Data-Answer) using MMTEL service subscriptions such as call forwarding and call barring. Such information is stored in IWF 20 for constructing an insert subscriber-data request to VPLMN MSC 110.

Next, vHLR 130 sends a MAP insert-subscriber-data request to MSC/VLR 110 with the MMTEL service subscription retrieved from HSS 190 in the previous step. MSC/VLR 110 responds with a MAP-Insert-Subscriber-Data result and vHLR 130 sends a MAP-Update-Location result to MSC/VLR 110 to complete the network registration to UE 70.

IWF 20 then triggers SGW 170 to establish a GTP tunnel for the Packet Data Protocol (PDP) context and "ims" APN by sending a GTP-C create-session-request. That GTP tunnel is later used to carry voice and SMS traffic. PGW 230 sends a Gx Credit Control Request (CCR) to PCRF 240, which responds with a Credit Control Answer (CCA). The PGW 230 sends a GTP-C create-session-response to the SGW 170, and the PDP context setting is completed.

IWF 20 then sends a SIP registration request to SGW 170, via PGW 230, to the IMS core to register the virtual UE in the IMS domain. That registration is necessary for the IMS Core to route MT-Voice and SMS to the virtual UE via the PGW 230 and SGW 170, and the IMS Core routes the Cx User-Authorized- to the HSS 190, which responds with a User Authorization Answer (UAA). Authorize subscriber registration by sending a request (UAR). In the embodiment of FIG. 3, the IMS core performs "early IMS authentication" by delegating the SIP registration request from IWF 20, SGW 170, and IWF 20 triggers TAS 220 to (UDR/UDA) to search subscriber MMTEL profile. SIP registration is completed by the IMS core sending a 200 OK to the SGW 170.

In another embodiment, the SGW 170 of the IWF 20 or the P-CSCF 210 of the HPLMN 60 IMS core inserts an "authentication-complete" parameter into the SIP registration request, and the serving call session control function (S-CSCF) 210 indicates that the authentication is complete. Suppose then.

MO-Voice Service

FIG. 5 shows a signaling diagram for a mobile originated (MO) voice call from UE 70. The UE 70 sends call control (CC) settings to the MSC 100, and the MSC 100 responds to the progress of the CC call and checks for supplementary services (such as call regulation). MSC 110 interrupts the call by sending an ISDN User Part (ISUP) Initial Address Message (IAM) to PSTN 290, which responds with an Address Complete Message (ACM). MSC 110 sends a CC call alert to UE 70. The call is routed to the destination and PSTN 290 responds with an ISUP Answer Message (ANM). MSC 110 sends CC connection to UE 70

The MO call is dropped when UE 70 sends a CC release to MSC 110, which sends an ISUP release (REL) to PSTN 290 and responds with a CC release signal to UE 70. The disconnect signal reaches the destination party. PSTN 290 responds with an ISUP Release Complete (RLC) and MSC 110 sends a CC Release Complete to UE 70. MSC 110 generates CDRs for billing.

Typically, if an exception occurs when a customized application for mobile network enhancement logic (CAMEL) triggering is activated in the subscriber MSC 110, the entire signal flow in the VPLMN 50 and HPLMN is not triggered. .

MT-Voice Service

FIG. 6 shows a signaling diagram for a mobile terminated (MT) voice call towards UE 70. The MT call arrives at the HPLMN60 IMS core where the subscriber is IMS registered. The IMS Core routes the SIP Invite to the UE (whose contact header was previously registered with the IMS Core during IMS registration) via the PGW 230, SGW 170, vGMSC 150. vGMSC 150 queries vHLR 130 for MAP-Send-Routing-Information (SRI). The VHLR 130 queries the MSC 110 of the VPLMN 50 with the MAP-Provided-Roaming Number (PRN) of the Mobile Station Roaming Number (MSRN). Once the MMSRN is received from the MSC 110, the vGMSC 150 routes the call (SIP invite) to the PSTN 295 with the called party number (SIP request-URI and "To" header) being the MSRN. PSTN 295 converts SIP calls to CS calls. The CS call arrives at MSC 110 (which assigned the MSRN number) of VPLMN 50, which further routes the call to UE 70 with CC configuration. UE 70 responds with a CC alert after the CC call is confirmed. MSC 110 sends an ISUP Address Complete (ACM) to PSTN 295. IBCF/vGMSC (180/150) receives SIP 183 session progress and is populated by SGW 170, PGW 230, IMS Core and TAS 220. The IMS Core P-CSCF 210 triggers the PCRF 240 to establish a dedicated bearer by sending an RxAA-Request (AAR). PCRF 240 sends a GxRe-Authentication-Response (RAR) to PGW 230. PGW 230 completes the dedicated bearer setup by sending a GTP-C generated bearer request to SGW 170. SGW 170 responds with a Create-Bearer-Response. PGW 230 returns a GxRe-Authentication-Response (RAR). PCRF 240 returns RxAA-Answer (AAA).

When the user answers the call on the UE 70, the UE 70 sends a CC connection to the MSC 110, which converts it into an ISUP Answer Message (ANM) and sends it to the PSTN 295, which sends it to the SGW 170, PGW 230, IMS core , and the IBCF/vGMSC (180/150) that populates TAS220.

The voice payload is bridged at UE 70, MSC 110, PSTN, IBCF, vGMSC, SGW 170, PGW 230, P-CSCF (in the IMS core) 210 and HPLMN PSTN 270.

In this embodiment, the PSTN 270 sending a SIPBYE causes the remote party to disconnect the call, which causes the PSTN 270 to populate the IMS core, TAS 220, PGW 230, SGW 170, vGMSC 150, IBCF 180, and PSTN 295. PSTN 295 sends an ISUP Release Complete (RLC) to MSC 110. MSC 110 sends a CC disconnection signal to UE 70. UE 70 responds with a CC release. MSC 110 sends an ISUP Release Complete (RLC) to PSTN 295. PSTN 295 sends a SIP OK to IBCF/vGMSC, which populates SGW 170, PGW 230, IMS Core and TAS 220. GTP-C Delete-Bearer-Request between SGW 170 and PGW 230, GxRe-Authentication-Request/Answer (RAR/RAA) between PGW 230 and PCRF 240, and P-CSCF 210 and PCRF 240 of IMS-Core. According to the Rx session-termination-request/answer (STR/STA) of the dedicated ceala, the MSC generates a CS-based CDR for billing. SGW 170 also generates PS-based CDRs for billing.

MO SMS

Figure 7 shows how the implementation of Mobile Originated (MO) SMS is possible. UE 70 sends RP-Data for SMS-Submission to MSC 110, which checks supplementary services (e.g. call regulation) and sends a MAP-MO-Forward-SM (MO-FSM) to vSMSC 140. . The vSMSC 140 converts the request into a SIP message and routes it to the IP Short Message Gateway (IPSMGW) in the SGW 230, PGW 230, HPLMN's IMS core, and TAS 220. The IPSMGW routes the SMS request to the local SMSC or SMS gateway for delivery to the recipient.

If the SMS is successful or unsuccessful, the IPSMGW sends an SMS-Status-Report SIP message to the IMS Core, PGW 230, SGW 170, vSMSC 140. vSMSC 140 converts the SIP message to a MAP-MT-Forward SM. MSC 110 sends RAP-Data for SM-Status-Report to UE 70. UE 70 sends an RP-Confirmation to MSC 110. MSC 110 sends the MAP-MT-Forward SM result to vSMSC 140. vSMSC 140 converts it to SIP200 OK and sends it to SGW 170, PGW 230, IMS Core, and TAS 220.

FIG. 8 shows a method how the implementation of Mobile Terminated (MT) SMS is possible. The IPSMGW in HPLMN 60 receives the MT-SMS and routes it to the IMS core in the form of a SIP message request. The IMS core routes the SIP message request to the UE 70 (where its contact header was previously registered with the IMS core during IMS registration) via the PGW 230, the SGW 170, and the vSMSC 140. The vSMSC 140 sends a MAP-Send-Routing-Information-for-SM (SRI-SM) to the VPLMN's MSC 110 address. VSMSC 140 converts the SMS request to a MAP-MT-Forward SM (MT-FSM) and sends it to vHLR 130. MSC 110 delivers the SMS to UE 70 by sending RP-Data-SMS-Delivery.

If the SMS delivery report is valid, the UE 70 sends RP-DATA for SMS-delivery report to the MSC 110. MSC 110 sends a MAP-MO-Forward-SM (MO-FSM) to vSMSC 140. vSMSC 140 converts the request into a SIP message and sends it to the IP Short Message Gateway (IPSMGW) in SGW 170, PGW 230, HPLMN's IMS core and TAS 220. TAS 220 returns SIP 200 OK to IMS core, PGW 230, SGW 170, and vSMSC 140. vSMSC 140 converts it to a MAP-MO-Forward SM result and sends it to MSC 110. MSC 110 sends an RP-Confirmation to UE 70.

Examples of hardware and software infrastructure

The invention can be implemented on a variety of platforms. Next, a preliminary foundation for information technology that can be utilized to enable the present invention is provided.

Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may be implemented as instructions stored on a machine-readable medium that may be read and executed by one or more processors. The machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (eg, a computing device). For example, machine-readable media can include read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, electrical, optical, acoustic or other forms of propagated signals ( (eg, carrier waves, infrared signals, digital signals, etc.), and others. Additionally, firmware, software, routines, and instructions may be described herein as performing certain actions. However, such descriptions are merely for convenience and such actions may not be performed by a computing device, processor, controller, or other device executing firmware, software, routines, instructions, etc. Please understand that this is a result of fact.

A machine-readable medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More specific examples (non-exhaustive list) of computer readable storage media include: an electrical connection comprising one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), fiber optics, portable compact disk read-only memory (CD-ROM), optical storage, magnetic storage, or any suitable combination thereof. Those with In the context of this document, a computer-readable storage medium is any non-transitory, tangible medium that contains or is capable of storing a program for use by or in conjunction with an instruction execution system, apparatus, or device. It may be. Storage and services may be commercial or remote, such as on the cloud with vendors operating under the Microsoft® AZURE, Amazon® WEB SERVICE, RACKSPACE, and KAMATERA brands.

A machine-readable signal medium may include a propagated data signal having machine-readable program code embodied, for example, in baseband or as part of a carrier wave. Such propagating signals can take any of a variety of forms including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A machine-readable signal medium is any machine-readable medium that is not a computer-readable storage medium and that can communicate, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. obtain. However, as noted above, due to circuit statutory subject matter constraints, the claims of the invention as a software product may not be embodied in a non-transitory software medium such as a computer hard drive, flash-RAM, optical disk, etc. It is something that

The hardware equipment may be general computing independent or telecommunications specific. Some equipment providers include those under the HUAWEI®, CISCO® Systems, NOKIA®, and QUALCOMM® brands.

Program code embodied on a machine-readable medium can be implemented using any suitable medium, including, but not limited to, wireless, wireline, fiber optic cable, radio frequency, or any combination of the foregoing. can be transmitted. Machine-readable program code that performs operations for aspects of the invention may be written in any combination of one or more programming languages. Java, C#, C++, Visual Basic, and other conventional procedural programming languages, such as object-oriented programming languages, the "C" programming language, or similar programming languages. Additional languages such as ERLANG (or Open Telecom Platform, OTP) may be used, or scripting languages such as PYTHON, LUA and PERL.

Aspects of the invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block in the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by machine-readable program instructions.

Glossary

Access Point Name (APN) refers to the gateway between a GSM, GPRS, 3G or 4G mobile network and other computer networks, often the public Internet. The APN identifies the packet data network (PDN) with which the mobile data user wishes to communicate. In addition to identifying the PDN, the APN can also be used to define the type of service.

The Application Function (AF) is a Charging Control (PCC) framework that provides the logical elements of 3GPP policies, as well as session related information for policies, and Charging Rules Function (PCRF) in support of PCC rule generation.

Attribute Value Pair (AVP) refers to an information element of a Diameter Protocol message. Each Diameter message includes multiple AVPs, such as a destination host AVP, a subscription IDAVP, a server name AVP, and a framed IP address AVP.

Diamiter is an authentication, authorization, and accounting protocol for computer networks.

A Diameter Routing Agent (DRA) is an element within a 3G or 4G (eg, LTE) network that enables real-time routing capabilities so that messages are routed between the correct elements within the network. DRA was launched by 3GPP to handle the growth of increasing diameter signaling traffic and sophistication of 4GLTE networks.

An evolved Node B (eNB or eNodeB) is a base station that terminates the air interface on the network side. It is responsible for all radio resource management. It is also responsible for allocating user traffic to downlink/uplink, security, and relaying of upper layer NAS (non-access stratum) signaling to the MME.

The Evolved World Terrestrial Radio Access Network (EUTRAN) is the radio (air interface) access architecture for LTE.

A fully qualified domain name (FQDN) is a domain name that defines its exact location in the Domain Name System (DNS) tree hierarchy.

The Gateway Mobile Switching Center (GMSC) is a function within the PLMN (Public Land Mobile Network). GMSC terminates PSTN (Public Switched Telephone Network) signaling and traffic formats. It converts this into the protocols used in mobile networks. For mobile terminated calls, the GMSC interacts with the HLR (Home Location Registration) and retrieves routing information.

General Packet Radio Service (GPRS) is a packet-oriented mobile data standard on the 2G/3G cellular telecommunications network Global System (GSM) for mobile communications.

The GPRS Tunneling Protocol (GTP) is defined by the 3GPP standards to operate General Packet Radio Service (GPRS) within 3G/4G networks.

HLR stands for Home Location Register, which is a database containing subscription data about subscribers authorized to use the GSM core network. HLRs store details for each SIM card issued by a mobile phone operator.

Home Public Land Mobile Network (HPLMN) means a network in which a mobile subscriber's profile is maintained. Mobile users roam on other networks (visits) and receive subscription information from HPLMN.

HSS implements HLR and Diameter Signaling. means Home Subscriber Service. HSS is a central database containing user-related information and subscription-related information. HSS functionality includes functionality such as mobility management, call and session establishment support, user authentication and access authorization. Its HSS is used in IMS, 4G while HLR is used in 2G, 3G.

IMS stands for IP Multimedia Subsystem, an architectural framework for standardizing voice distribution and other multimedia services in IP packet-switched networks.

IMSI stands for International Mobile Subscriber Identity Number. It is a specification used to uniquely identify subscribers to mobile phone services. It is used within GSM networks and is adopted on almost all cellular networks. The IMSI is a 50-bit field, typically 15 digits, that identifies the home country and carrier of the phone. This 15-digit number has two parts. The first part consists of 6 digits in North American standards and 5 digits in European standards. It identifies the GSM network operator in the particular country with which the subscriber maintains an account. The second part is assigned by the network operator to uniquely identify the subscriber. For GSM, UMTS and LTE networks, this number is provided either directly in the SIM card, in the phone for CDMA2000, or on the R-UIM card (CDMA2000 analogue for GSM SIM cards).

Inbound roaming means that subscribers of other networks "visit" into the local (home) network, but can use the local network to make calls, send messages, etc. Inbound roaming services allow subscribers from other operators to access local networks and services.

The Interconnection Border Control Function (IBCF) is a border control between various service provider networks and provides IMS network security with respect to signaling information. It enables communication between IPv4 and IPv6 SIP applications, allowing control of transport plane functions, hiding network topology, screening SIP signaling, selecting optimal signaling interconnections, and creating billing data records. do.

The Inquiry Call Session Control Function (I-CSCF) is responsible for forward routing of SIP messages to the appropriate S-CSCF (Serving CSCF) for a given subscriber. It is a key element in IMS roaming methodology.

An IP Short Message Gateway (IPSMGW) is an IMS application server that handles SIP-based messaging services for IMS subscribers.

Long-Term Evolution (LTE) is a standard for wireless broadband communications for mobile devices and data terminals based on GSM/EDGE and UMTS/HSPA technologies.

A media gateway (MGW) handles the media plane (voice) in a distributed switch.

The Media Gateway Control Function (MGCF) facilitates call control by interfacing the PS domain to the circuit switched domain when interworking between the IMS and the PSTN is required.

The Mobile Application Part (MAP) is used to access the Home Location Register (HLR), Visitor Location Register (VLR), Mobile Switching Center, and other components of the mobile network infrastructure. , which is the SS7 protocol

Mobile Switching Center (MSC) refers to the primary service distribution node for GSM/CDMA and is responsible for routing voice calls and SMS and other services. The MSC connects and releases end-to-end connections, manages mobility and handover requirements during calls, and oversees billing and real-time prepaid account monitoring.

Mobility Management Entity (MME) is a standardized component within Long Term Evolution (LTE) systems. The MME provides mobility session management for LTE networks and supports authentication, handover, and roaming between subscribers and other networks.

The MSISDN is the Mobile Station International Subscriber Directory Number that is provided to mobile device subscribers for making calls. It is the mapping of a phone number to a SIM card (or CDMA2000 directly in hardware) in a mobile device or cellular phone, which is the number that would normally be dialed to connect a call to the mobile device. . A SIM card has a unique IMSI that does not change over time (eg, phone number portability), but the MSIDN changes over time.

Outbound roaming typically occurs when a subscriber moves to another country. The subscriber's home network has a contract with the network that the subscriber is visiting in another country. This agreement allows subscribers to use their mobile phones to make calls and send messages on their visited networks. Subscribers "roam outbound" with respect to their home network provider. At the same time, considering the visited network, the subscriber is "inbound roaming". In other words, inbound roaming services allow subscribers to access local networks and services from other operators. Outbound roaming services allow subscribers to access other operators' networks and services from their local network.

A Packet Data Network Gateway (PGW) is used to assign an IP address to a user equipment during default bearer configuration.

The Policy and Charging Rules Function (PCRF) is a real-time designated software node that supports service data flow detection, policy enforcement, and flow-based charging.

A Proxy Call Session Control Function (P-CSCF) is a SIP proxy that is the first point of contact for user equipment in a mobile network. All SIP traffic to or from user equipment must go through the P-CSCF. It acts as an entry and exit point to and from the service provider's IMS domain for IMS clients.

Public Switched Telephone Network (PSTN) refers to a circuit-switched network primarily used for worldwide voice communications.

The S6a interface is the diameter-interface between the MME and the HSS in the LTE network that provides messages and procedures for telephony equipment.

The Serving Call Session Control Function (S-CSCF) is the primary node in IMS handling session control. A subscriber is assigned an S-CSCF for the period of its IMS registration to facilitate the routing of SIP messages.

A serving gateway (SGW) routes and forwards user data packets. The SGW manages and stores the UE context, such as IP bearer service parameters and network internal routing information.

The Serving GPRS Support Node (SGSN) is the main component of a GPRS network that handles all packet-switched data within the network.

Session Initiation Protocol (SIP) is a protocol designed to establish, maintain, and terminate multimedia sessions. SIP has been adopted as the primary signaling protocol in different network architectures. This SIP is deployed in 3GPP IMS (IP Multimedia System).

A Signal Transmission Point (STP) is a node within an SS7 network (2G, 3G) that routes signaling messages based on a destination point code within the SS7 network (2G, 3G).

Telephone Application Server (TAS) refers to a component used in a telecommunications network operator's core network to provide telephony applications and additional multimedia functionality. The TAS provides service logic that calls the media server to provide call progress tones and announcements. When multiple calls originate or terminate on the PSTN, the TAS provides SIP signaling to the MGCF to convert the PSTN TDM voice bitstream to an IP RTP stream and convert it into the corresponding IP Telephone Internet Protocol (IP ) instructs the media gateway to point to the address.

World Mobile Telecommunication System (UMTS) Terrestrial Radio Access Network (UTRAN) refers to the radio technology used between mobile terminals and 3G UMTS base stations

User equipment (UE) refers to a mobile device capable of connecting to a cellular communication network.

Virtualized Mobility Management Entity (vMME) refers to a virtualized implementation of a network's main control plane entity that maintains the mobility state of user equipment in the network.

Visitor Location Register (VLR) refers to a database that stores data regarding mobile phones that have recently joined a particular area of a mobile operator's network. The VLR communicates with the HLR to record roamed mobile phones and determine whether the mobile phone is a permanent or temporary subscriber.

Visited Public Land Mobile Network (VPLMN) refers to the network in which a mobile subscriber roams when leaving the Home Public Land Mobile Network (HPLMN).

The above effects and the matters evident from the above disclosure can be obtained efficiently. Since certain changes may be made in the configuration described above without departing from the scope of the invention, all matter contained in the above disclosure or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. is intended to be interpreted as

10 Interworking Function (IWF)
30 CS roaming
50 Visited Public Land Mobile Network (VPLMN)
60 Home Public Land Mobile Network (HPLMN)
70 User Equipment (UE)
80 UTRAN
90 EUTRAN
100 Mobility Management Entity (MME)
105 SGSN
110 Mobile Switching Center (MSC)
120 Diameter Routing Agent (DRA)
130 Virtual Home Location Register (vHLR)
140 Virtual Short Message Service Center (vSMSC)
150 Virtual Gateway Mobile Switching Center (GMSC)
160 Virtual Mobility Management Entity (vMME)
170 Serving Gateway (SGW)
171 SGW
180 Interconnection Border Control Function (IBCF)
190 Home Subscriber Server (HSS)
200 Short Message Service Center (SMSC)
210 IP Multimedia Subsystem (IMS) Core
220 Telephone Application Server (TAS)
230 Packet Data Network Gateway (PGW)
240 Policy and Charging Rules Function (PCRF)
250 Mobile Originated (MO) Voice Call
270 PSTN
280 Destination Party
290 PSTN
295 PSTN
300 MT-Call
310UE

Claims (20)

A Home Public Land Mobile Network (HPLMN) with a Voice over Long Term Evolution (VoLTE) infrastructure can now , to provide voice and short message service (SMS) for subscriber user equipment (UE) roaming within a visited public land mobile network (VPLMN) having a circuit switched (CS) infrastructure. an interworking function (IWF), said IWF comprising:
A Diameter Routing Agent (DRA) is communicatively coupled to the VPLMN and the HPLMN, the DRA configured to intercept and mediate messages between the VPLMN and the HPLMN. thing;
a virtual home location register (vHLR) communicatively coupled to a virtual short message service center (vSMSC), a virtual gateway mobile switching center (vGMMSC), and a virtual mobility management entity (vMME);
a serving gateway (SGW) communicatively coupled to the vSMSC and vMME;
An Interconnect Border Control Function (IBCF) is communicatively coupled to the vGMSC and converts a Mobile Application Part (MAP) Update Location Request from the VPLMN to a First Diameter-Update Location Request (ULR) request to the subscriber phone. A service subscription profile is retrieved by the vMME from the Home Subscriber Service (HSS) using a second Diameter User Data Request (UDR) request, and the General Packet Radio Service Tunneling Protocol (GTP) session is Established between a Serving Gateway (SGW) of an IWF and a Packet Network Data Gateway (PGW) of an HPLMN, said PGW receives a session initiation protocol from an IP Multimedia Subsystem (IMS) core of said HPLMN. configured to send and receive (SIP) signaling and voice payloads, the subscriber profile is retrieved from the HSS and the MAP inserts subscriber data to the Mobile Switching Center (MSC) and Visitor Location Register (VLR). (ISD) request to enable the VPLMN to provide supplementary services, the IWF's vSMSC bridges to the VPLMN's MSC and IP Short Message Gateway (IPSMGW), and the VPLMN provides the SMS service. Using a GTP tunnel established between the IWF's SGW and the HPLMN's PGW, the IWF's vGMSC communicates with the VPLMN's MSC and VLR and the HPLMN's IMS. bridging the core and enabling the UE to receive mobile terminated (MT) voice calls. The IWF of claim 1, wherein the DRA mediates ULR messages by replacing an originating host attribute value pair (AVP) with a hostname of the vMME. The IWF of claim 1, wherein the IWF converts a MAP-Send-Authentication-Information from a VPLMN SGSN or MSC/VLR to a Diameter Authentication-Information-Request to the HSS. 2. The IWF of claim 1, wherein the IWF converts MAP-Update-Gprs-Location from VPLMN SGSN to Diameter-Update-Location-Request to HSS. The IWF of claim 1, wherein the IWF sends a SIP registration from a virtual UE to the IMS core to perform SIP registration. 10. The IMS is configured to use early IMS authentication by trusting the SIP registration sent from the SGW of the IWF, thereby skipping multimedia authentication (MAR/MAA) processing. IWF as described in. the IWF of the SGW or the P-CSCF of the IMS core inserts an authentication-complete parameter into the SIP registration request, whereby the S-CSCF skips multimedia authentication (MAR/MAA) processing; IWF according to claim 1. The IWF of claim 1, wherein the IWF enables the VPLMN to provide the SMS service to the UE using a CS method. The IWF of claim 1, wherein the IWF enables CS to roam towards the VPLMN and VoLTE to roam towards the HPLMN. A home public land mobile network (HPLMN) with a Voice over Long Term Evolution (VoLTE) infrastructure requires Internet Protocol Multimedia Subsystem (IMS) registration between the VPLMN and the HPLMN. Provide voice and short message service (SMS) to subscriber user equipment (UE) roaming within a visited public land mobile network (VPLMN) with a circuit-switched (CS) infrastructure without Methods that allow this include:
providing an interworking function (IWF) having a Diameter Routing Agent (DRA) communicatively coupled to the VPLMN and HPLMN, the DRA intercepting messages between the VPLMN and HPLMN; configured to mediate;
Within the IWF, a virtual home location register (vHLR) is provided, and the vHLR is connected to a virtual short message service center (vSMSC), a virtual gateway mobile switching center (vGMSC), and a virtual mobility management entity (vMME). communicatively coupled;
providing a serving gateway (SGW) within the IWF, the SGW communicatively coupled to the vSMSC and vMME;
providing an Interconnect Border Control Function (IBCF) within the IWF, the IBCF communicatively coupled to the vGMSC, wherein a mobile application part (MAP) update location request is transmitted from the VPLMN to a first diameter update location; The subscriber telephone service subscription profile is retrieved by the vMME from the Home Subscriber Service (HSS) using a second Diameter User Data Request (UDR) request and the general packet A Wireless Service Tunneling Protocol (GTP) session is established between the IWF's Serving Gateway (SGW) and the HPLMN's Packet Network Data Gateway (PGW), where the PGW performs an IP multimedia the subscriber profile is retrieved from the HSS and configured to send and receive Session Initiation Protocol (SIP) signaling and voice payloads from the subsystem; a subscriber profile is retrieved from the HSS; register (VLR) into a MAP Insert-Subscriber-Data (ISD) request to enable the VPLMN to provide supplementary services, and the vSMSC of the IWF connects the MSC of the VPLMN and the HPLMN an IP short message gateway (IPSMGW) of the IWF to enable the VPLMN to provide SMS services to the UE, and a vGMSC of the IWF is established between the SGW of the IWF and the PGW of the HPLMN. bridging to the MSC and VLR of the VPLMN and the IMS core of the HPLMN using a GTP tunnel to enable the UE to receive mobile terminated (MT) voice calls. 11. The method of claim 10, wherein the DRA mediates ULR messages by replacing an originating host attribute value pair (AVP) with a hostname of the vMME. 11. The method of claim 10, wherein the IWF converts MAP-Send-Authentication-Information from a VPLMN SGSN or MSC/VLR into a Diameter Authentication-Information-Request to the HSS. 11. The method of claim 10, wherein the IWF converts a MAP-Update-Gprs-Location from a VPLMN SGSN into a Diameter Update-Location request to the HSS. 11. The method of claim 10, wherein the IWF sends a SIP registration from a virtual UE to the IMS core to perform SIP registration. 10. The IMS is configured to use early IMS authentication by trusting a SIP registration sent from an SGW of the IWF, thereby skipping multimedia authentication (MAR/MAA) processing. The method described in. The SGW of the IWF or the P-CSCF of the IMS core inserts an authentication-complete parameter into the SIP registration request, whereby the S-CSCF skips multimedia-authentication (MAR/MAA) processing. , the method according to claim 10. 11. The method of claim 10, wherein the IWF enables the VPLMN to provide the SMS service to the UE using a CS method. 11. The method of claim 10, wherein the IWF enables CS roaming towards the HPLMN and VoLTE roaming towards the HPLMN. An outbound roamer can roam the network in a visited public land mobile network (VPLMN) without the need for a Voice over Long Term Evolution (VoLTE) roaming agreement with the home public land mobile network (HPLMN) operator. A system for enabling the use of switched (CS) voice, comprising:
a Diamiter Routing Agent (DRA) that intercepts and routes Diamiter S6a/s6d messages between the VPLMN Mobility Management Entity (MME) and the HPLMN Home Subscriber Server (HSS);
a virtual home location register (vHLR) providing subscriber registration services to a mobile switching center (MSC) within said VPLMN;
a virtual mobility management entity (vMME) that performs Long Term Evolution (LTE) registration to the HSS in the HPLMN;
a virtual gateway mobile switching center (vGMSC) that delivers mobile terminating calls (MT-calls) to mobile terminals;
a serving gateway (SGW) that encapsulates IP packets into a general packet radio service tunneling protocol (GTP) tunnel towards a packet data network gateway (PGW) in said HPLMN; and a public switched telephone network. (PSTN), the Interconnected Border Control Function (IBCF), which acts as a border controller, allows CS to roam towards the VPLMN and VoLTE to roam towards the HPLMN. Outbound roamers can switch circuits in a visited public land mobile network (VPLMN) without requiring a Voice over Long Term Evolution (VoLTE) roaming agreement with the home public land mobile network (HPLMN) operator. (CS) A system for enabling the use of SMS services, including:
Diameter Routing Agent (DRA) that intercepts and routes Diameter S6a/s6d messages between the VPLMN Mobility Management Entity (MME) and the HPLMN Home Subscriber Server (HSS);
a virtual home location register (vHLR) providing subscriber registration services to a mobile switching center (MSC) within said VPLMN;
a virtual mobility management entity (vMME) that performs Long Term Evolution (LTE) registration to the HSS in the HPLMN;
a virtual short message service center (vSMSC) that receives and routes mobile originated SMS (MO-SMS) from a mobile device and delivers mobile terminated SMS (MT-SMS) to said mobile device;
a serving gateway (SGW) that encapsulates IP packets into a general packet wireless service tunneling protocol (GTP) tunnel towards a packet data network gateway (PGW) within the HPLMN; and a public switched telephone. An Interconnection Border Control Function (IBCF), system acting as a border controller to network (PSTN) connectivity, enables CS roaming towards the VPLMN and enabling VoLTE to roam towards the HPLMN.